Why Can't I get my DTI to Repeat

[mikey]

Okay, so the indicator repeats with the solid holder. Sounds like you need a better holder, maybe like this one.

I got frustrated when doing concentricity checks with the articulating arm Nogas on my lathe and mill - too much movement in the holder. I switched to my old 2-arm Mitutoyo and the problems went away. The problem with the older designs is that it is a major hassle to adjust the indicator to the work. The Noga design with the fine adjuster at the base makes it easy, and the central locking mechanism makes it easy to position the indicator close to the work. Plus, its less than 40 bucks shipped from Amazon! You might consider it.

 

[ddickey]

Mike it does repeat but every third rotation.
Noga ordered.

 

[darkzero]

Pic of the set up.
View attachment 293240

Your Noga, does it have the fine adjust on top (FAT) or at the base (FAB)? I'm not a fan of the FAT. Have to snug the clamp pretty good so it doesn't move & keep the tension on the fine adjust closer to maxed out. Even then it still can move easily through the spring loaded adjustment mechanism. The spring they use is way too soft. I got rid of all my NOGA FATs (except for 1) & only use the FAB. The FAB work so much better.

 

[darkzero]

Mike it repeats every third rotation.

That's so weird! As much as I don't like the Noga FAT they still wouldn't give those kind of results, at least I never encountered it. They work fine, just very finiky.

Gonna grab a bag of popcorn & wait for the outcome.

 

[mikey]

Mike it repeats every third rotation.

Then I must admit that I don't know what the hell is going on. Something is moving. If the indicator cannot move and the work cannot move then it must repeat unless the indicator is junk. How do multiple indicators develop a case of junk? Wish I was there with you, Duane.

 

[ddickey]

It's a FAT.

 

[ddickey]

IDK Mike.
It is possible that they are all junk.
Tomorrow I may try to take a video for your viewing pleasure.

 

[darkzero]

Highly unlikely that all the indicators are bad especially if they all give the same type.of reading.

If you take a test cut on a piece of material, does it machine fine, no chatter, etc? If it machines fine which I assume yes, indicate what you just cut, does it read zero then? If it doesn't read zero try mounting the indicator mag base directly on the bed ways instead of somewhere on the carriage/cross slide/compound. Although if you don't have any issues machining I don't see how it could be carriage related.

 

[ddickey]

Yes it's machining fine.
I will try that tomorrow and post back.

 

[hman]

John,
Do you mean something like this?

Yes, that's what I meant.

I will say three revolutions and it finally stumbled back to zero.

Frubadubadub, Dude. You've got a genuine case of the gremlins. Quoting Mikey, "How do multiple indicators develop a case of junk?"

OK... just for fun, try one more thing. Using the setup pictured, and without moving anything else, try withdrawing the indicator point and gently letting it return to contact. Should come back to the same reading. If it does (as I expect it will), I'm out of ideas. If it doesn't, you're on the way toward understanding the problem.
-or-
Try gently moving the extended stem up and down. If it moves, the irregularity in readings may be due to the tip "falling off" the peak of the test rod as it makes contact above, on and below center.